Re: [PATCH 3/7] iommu/arm-smmu: Add tlb_sync implementation hook

From: Robin Murphy
Date: Mon Sep 02 2019 - 09:00:13 EST

On 30/08/2019 23:49, Krishna Reddy wrote:
+ if (smmu->impl->tlb_sync) {
+ smmu->impl->tlb_sync(smmu, page, sync, status);

What I'd hoped is that rather than needing a hook for this, you could just override smmu_domain->tlb_ops from .init_context to wire up the alternate .sync method directly. That would save this extra level of indirection.

Hi Robin, overriding tlb_ops->tlb_sync function is not enough here.
There are direct references to arm_smmu_tlb_sync_context(), arm_smmu_tlb_sync_global() functions.
In arm-smmu.c. we can replace these direct references with tlb_ops->tlb_sync() function except in one function arm_smmu_device_reset().
When arm_smmu_device_reset() gets called, domains are not initialized and tlb_ops is not available.
Should we add a new hook for arm_smmu_tlb_sync_global() or make this as a responsibility of impl->reset() hook as it gets
called at the same place?

Ah, right, I'd forgotten about the TLB maintenance on reset. Looking again, though, I think you might need to implement impl->reset anyway for the sake of clearing GFSR correctly - since the value read from the base instance technically may not match whatever bits might happen to be set in the other instances - so I don't see any issue with just calling nsmmu_tlb_sync() from there as well.